This invention relates to a dot printing device with a function of printing double height characters.
The dot printing device usually has a printing head having N head pins arranged in a row. During printing, the printing head is moved at a constant speed in a direction perpendicular to the head pin row, while the individual head pins are selectively driven according to dot data for a character to be printed which is provided from a character generator. It has been well known in the art to print some of the characters to be printed as double width characters by doubling the width of each character or as double height characters by doubling the height of each character.
Meanwhile, it is sometimes required to print an underline not only with ordinary size characters but also with double height characters. In the prior art, an underline printing signal is provided separately from character data. That is, the underline is printed in fixed form irrespective of the type of characters which are printed together with it. Where a single head pin is used for printing an underline, for instance, the underline is printed in a well-balanced state in case it is printed with ordinary size characters, but when the underline is printed with double height characters, it looks rather thin compared to the double height characters so that the balance of the print as a whole is lost.